annonacin and Parkinsonian-Disorders

Complex I is the first protein component of the mitochondrial respiratory chain and as such plays a crucial role in ATP production and mitochondrial function in general. Mitochondrial dysfunction has been identified in a number of neurodegenerative diseases. In some of these the mitochondrial abnormality is primary and in others secondary. Mitochondrial toxins are capable of producing relatively selective neuronal cell death and have been used to produce models of human neurodegenerative diseases e.g. 1-methyl 4-phenyl 1,2,3,6 tetrahydropyridine (MPTP) for Parkinson's disease, and 3-nitropropionic acid for Huntington's disease. Annonacin, an ingredient of local soursop, is a Complex I inhibitor and has been incriminated as the cause of a parkinsonian tauopathy disorder in Guadeloupe. A systematic analysis has identified several environmentally available potent lipophilic Complex I inhibitors that can induce neuronal cell death in striatal cultures and somatodendritic redistribution of tau protein. It is possible that these compounds may contribute to the pathogenesis of neurodegenerative disorders, although further work must be done to confirm their potential participation in pathogenesis.

Topics: Animals; Cell Death; Disease Models, Animal; Electron Transport Complex I; Environmental Pollutants; Furans; Humans; Huntington Disease; Lactones; Mitochondria; Neurodegenerative Diseases; Neurons; Parkinsonian Disorders; Tauopathies

On the French West Indian island of Guadeloupe, atypical parkinsonian patients represent two-thirds of all cases of parkinsonism, which is exceptionally frequent compared to epidemiological data from European countries where atypical parkinsonism accounts for only approximately 5% of all cases. The clinical entity was a unique combination of levodopa-resistant parkinsonism, tremor, myoclonus, hallucinations, REM sleep behavior disorder and fronto-subcortical dementia. Based on the presence or the absence of supranuclear gaze palsy, two subgroups of patients were distinguished. In patients with oculomotor signs that came to autopsy, neuronal loss was found to predominate in the substantia nigra and the striatum but other brain areas were also affected, including the frontal cortex. In addition, tau-containing lesions were detected throughout the brain. Epidemiological data suggested a close association of the disease with the regular consumption of soursop, a tropical annonaceous plant. Experimental studies performed in midbrain cell cultures identified annonacin, a selective mitochondrial complex I inhibitor contained in the fruit and leaves of soursop, as a probable etiological factor. Consistent with this view, chronic administration of annonacin to rats through Alzet osmotic minipumps showed that annonacin was able to reproduce the brain lesions characteristic of the human disease.

Topics: Animals; Electron Transport Complex I; Furans; Guadeloupe; Humans; Lactones; Mitochondria; Parkinsonian Disorders

In Guadeloupe, epidemiological data have linked atypical parkinsonism with fruit and herbal teas from plants of the Annonaceae family, particularly Annona muricata. These plants contain a class of powerful, lipophilic complex I inhibitors, the annonaceous acetogenins. To determine the neurotoxic potential of these substances, we administered annonacin, the major acetogenin of A. muricata, to rats intravenously with Azlet osmotic minipumps (3.8 and 7.6 mg per kg per day for 28 days). Annonacin inhibited complex I in brain homogenates in a concentration-dependent manner, and, when administered systemically, entered the brain parenchyma, where it was detected by matrix-associated laser desorption ionization-time of flight mass spectrometry, and decreased brain ATP levels by 44%. In the absence of evident systemic toxicity, we observed neuropathological abnormalities in the basal ganglia and brainstem nuclei. Stereological cell counts showed significant loss of dopaminergic neurones in the substantia nigra (-31.7%), and cholinergic (-37.9%) and dopamine and cyclic AMP-regulated phosphoprotein (DARPP-32)-immunoreactive GABAergic neurones (-39.3%) in the striatum, accompanied by a significant increase in the number of astrocytes (35.4%) and microglial cells (73.4%). The distribution of the lesions was similar to that in patients with atypical parkinsonism. These data are compatible with the theory that annonaceous acetogenins, such as annonacin, might be implicated in the aetiology of Guadeloupean parkinsonism and support the hypothesis that some forms of parkinsonism might be induced by environmental toxins.

Topics: Adenosine Triphosphate; Animals; Behavior, Animal; Cell Count; Corpus Striatum; Electron Transport Complex I; Furans; Gliosis; Guadeloupe; Infusions, Intravenous; Lactones; Male; Mitochondria; Neurodegenerative Diseases; Neurons; Parkinsonian Disorders; Plant Extracts; Rats; Rats, Inbred Lew; Substantia Nigra